As is well known, a phased array radar includes an antenna with an array of identical radiating elements, such as waveguides, horns, slots, or dipoles. Phased array radars typically include a power supply having electronic means for altering the phase of power which is fed to each of the radiating elements. By properly controlling the alteration or shift in the phase of this power at each radiating element, the shape and direction of the radiation pattern can be altered without mechanical movement and with sufficient rapidity to be made on a pulse-to-pulse basis.
In general, phased array radars are extremely sophisticated electronic devices which incorporate precision components that will make the radar capable of achieving high target resolution with minimal delays in response time. Obviously, in order to achieve these capabilities the interaction between various components in a phased array radar must be carefully engineered. In particular, the interaction of various components with the phase shifter elements must be carefully engineered. Indeed, in order to increase precision, it is normally the case that each phase shifter is connected directly to the power feed and has a dedicated driver. This is so in order to minimize any additive effect the phase shifters may introduce into the radar system. At millimeter wave frequencies, however, the physical size of the components become so diminutive that their physical interconnection can pose a significant problem. There are, however, many potential applications for phased array radars using millimeter wave frequencies where relatively slower response times are tolerable, and where high target resolution is not essential.
An example where the performance characteristics of a phased array radar can be somewhat relaxed is a collision avoidance radar for relatively slow moving vehicles. In such a case, the ability of a phased array radar to change the direction of its radiated beam and thereby sweep across a particular area is still important. Some delay in response time, however, may be acceptable. Further, it will typically be the case that lower signal to noise ratios can be tolerated. In sum, the present invention recognizes there are many applications where a phased array radar can be extremely useful even though it may have less precise performance capabilities than are typically necessary for other, more specific, applications.
With the above in mind, the activation of individual phase shifters between the power feed and each of the radiating elements of the antennas became a design consideration of major importance to the present invention. With the knowledge that a circularly polarized wave is easily influenced by a magnetic flux field, the present invention recognized that though there are some inherent losses involved, each phase shifter in a phase shifter subarray need not have a dedicated driver. Specifically, the present invention recognizes that a plurality of phase shifter elements can be ganged together and differentially influenced by a common flux field.
In light of the above it is an object of the present invention to provide a phase shifter subarray for use in directing the beam of a phased array antenna which consolidates similar type components in order to simplify the interaction of different components. Another object of the present invention is to provide a phase shifter subarray for use in directing the beam of a phased array antenna which uses a single current mode driver to accomplish deflection of the radiated beam by driving all of the phase shifter elements in series. Still another object of the present invention is to use a common electrical coil for creating a flux field that differentially influences the phase shifters in the subarray to direct radiation from the antenna. Yet another object of the present invention is to provide a phase shifter subarray for use in directing the beam of a phased array antenna which tolerates relatively low signal to noise ratios during target acquisition. Another object of the present invention is to provide a phase shifter subarray for use in directing the beam of a phased array antenna which is reliable for use as a collision avoidance radar on relatively slow moving vehicles. Still another object of the present invention is to provide a phase shifter subarray for use in directing the beam of a phased array antenna which is relatively easy to manufacture, is simple to use, and is comparatively cost effective.